In tuning a string instrument, such as a guitar, mandolin, etc., the tension on each string is individually adjusted to bring the tone emitted into harmony with that of each of the others. This typically involves manually turning a peg attached to the string so as to put more, or less, tension on the string and thereby increase or decrease the frequency of vibration. This is a painstaking process, so that once an instrument is tuned, the tone emitted by a particular string is varied only by the musician pressing the string against the frets spaced along the finger board. When playing such an instrument, the musician sometimes desires to create a distinctive sound. Heretofore, such sounds have been limited to the final note of a musical composition or, in the case of an electric guitar, a note which is held for several beats. With an acoustic instrument a single peg can be adjusted by the musician with one hand to vary the pitch of a string while it is strummed with the other hand. This technique is occasionally employed, but it is limited to situations where the instrument can be retuned immediately thereafter. In the case of an electric guitar, this effect can be achieved by manipulation of a handle on the body of the instrument with the hand that strikes the note or chord. In either case, the normal playing action of the musician is interrupted, since one hand or the other is required to produce the distinctive sound instead of continuing to play the instrument in the usual manner.